1. Field of the Invention
The present invention relates to the field of liquid crystal display, and in particular to an illuminance adjusting method of a liquid crystal photo alignment irradiation machine.
2. The Related Arts
Liquid crystal displays (LCDs) have numerous advantages, such as thin device body, less power consumption, and being free of radiation, and is thus widely used. Most of the flat panel display devices available in the market are backlighting liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The operation principle of the liquid crystal display panel is that liquid crystal molecules are arranged between two parallel glass substrates and electricity is selectively applied to the glass substrates to control change of the orientation of the liquid crystal molecules in order to refract out the light from a backlight module for formation of an image.
Alignment control techniques are one of the most important essential techniques of the manufacture of liquid crystal display. The quality of image displayed on a liquid crystal display is related to whether the alignment of liquid crystal is done good or bad and high quality images can be presented only when the liquid crystal material of a panel shows stable and homogeneous alignment. Thin layers that are commonly used to align the liquid crystal molecules in a predetermined direction are referred to as alignment layers.
Referring to FIG. 1, the so-called HVA (High-Voltage-Activated) photo alignment is referred to irradiation of UV (Ultraviolet) light 700 to promote reaction of monomers 500 contained in the polymer inside a panel, under the condition of applying electrical voltage to substrates 100, so as to achieve the purposes of aligning the liquid crystal 300. Heretofore, HVA photo alignment techniques have been widely applied to high generation TFT-LCD business. To ensure that a specific alignment angle can be obtained by having liquid crystal irradiated with UV light without generating mura (which is referred to a phenomenon of various traces formed due to inhomogeneous brightness of a displaying device), irradiation homogeneity of UV light is a key factor. The UV light used in HVA photo alignment techniques is set to have illuminance within 85±10% mW/cm2. Heretofore, a UV lamp mounting frame of an alignment UV liquid crystal irradiation machine (UVM) is set at a fixed distance from a surface of a substrate support stage. However, with the use of the irradiation device, the illuminance on the surface of the stage will get deteriorated. The conventional UVM facility adopts two ways to increase the illuminance of the stage surface:
One is to increase the output power of the UV lamp in order to increase the illuminance of the stage surface. However, this shortens the lifespan of the UV lamp. The lifespan of the UV lamp may be reduced from 3000 h to 1500-2000 h.
The other one is to make minute adjustment of the orientation of the surrounding emission plates. However, this way only works for minute adjustment of illuminance and homogeneity of the illuminance and cannot greatly increase the illuminance.